The subject invention is directed toward the art of book binding machines in general and, more particularly, to an improved apparatus for extracting and opening signatures for placement on a saddle gatherer.
Many different apparatus are used for extracting signatures from a supply thereof and depositing them on an endless conveyor which transports gathered stacks of the signatures to further processing equipment. One of the more typical types uses vacuum cups to deflect the bottom signature from a stack to a position where clamping means on a rotating extractor drum can grip the folded back edge of the signature. As the extractor drum rotates, it pulls the signature from the stack and carries it around the drum to a stop position. At the stop position, the clamping means on the extractor drum release and grippers on a spreader drum engage a cut front edge of the signature and pull it away from the extractor drum.
Rotation of the spreader drum delivers the signature to an opener drum where the cut front edge is gripped by grippers associated with the spreader drum. With the signature engaged by the grippers of both the extractor drum and the opener drum, the signature is opened to an inverted V-shape as the drums rotate in opposite directions.
As the signature completes its passage through the nip area between the spreader and opener drums, the grippers release and the signature falls to a saddle from which it is gathered together with other signatures and conveyed to a stapling or stitching machine.
The typical prior art machine is significantly more complex than described above. Generally, for example, various "dipper" or "wiper" elements must be coordinated with the movement of the drums. These elements engage the signature to support or position it for proper engagement by the grippers on the succeeding drum. In addition, because of their orientation and interrelationships, the extractor drums and the spreader drums have interengaged disk sections and differing diameters. This requires that the drums be driven at different speeds and, further, that there be different gripper designs on each drum. All of the noted factors create mechanical and structural complexities and increase the costs of the units.